Shortcomings of Basing Radical Stabilization Energies on Bond Dissociation Energies of Alkyl Groups to Hydrogen

Abstract

Stabilization energies (SE(H)) of carbon radicals (R(*)) are traditionally defined as the difference between the bond dissociation energy (BDE) of CH(3)-H, as a reference point, and of R-H. The term "stabilization energy" implies that it is an intrinsic property of the radical and a quantitative measure of stability. Applicable only to carbon-centered radicals, SE(H) stabilization energies are not transferable and cannot be used to estimate carbon-carbon BDE[R-R'], symmetrical BDE[R-R], or any other BDE[R-X]. SE(H) values by themselves are neither an intrinsic property nor a quantitative measure of stability. There is available an alternative that is not limited only to carbon-carbon and carbon-hydrogen bonds, does not depend on any one particular molecule or BDE as a reference point, and is accurate with several hundred different types of bonds.